TFS321_0106 Datasheet, PDF (2/3 Pages) Vectron International, Inc – Application Note

Ltp: tft025
VI TELEFILTER
version 1.0
Application Note
L1 = L2 = 72.6 nH, C1 = C2 = 1.43 pF, L3 = 175 nH
50 Ohm Test circuit 2
TFS 321
19.06.2001
2/3
C1
5
C2
1
L1
SAW
L2
3
2, 4, 6, 7, 8
L3
The theoretical values of the stated elements are:
C1 = C2 = 3.38 pF, L1 = L2 = 53 nH, L3 = 175 nH
3. Matching on PCB
The theoretical matching was done without consideration of parasitics. The elements which
have to be used on the PCB are slightly different from the stated above.
For example for our PCB with 50 Ω test circuit 1 we had to split the serial inductors in two
elements to get identical results compared to our golden fixture using E12 series inductors.
L1 = 47 nH + 27 nH
L2 = 47 nH + 27 nH
C1 = C2 = 0 pF
L3 = 100 nH
All other components are 0 Ω jumpers.
But if the parasitics on the customer board (mentioned parasitics, additional parasitics of
active parts) are different to this PCB the matching elements have to be slightly adjusted.
Both in line and shunt elements change both pass band tilt and pass band ripple. But
- The in line coils mainly influences the pass band ripple a decrease of the inductance of the
in line coils will decrease pass band ripple or change a round pass band shape towards a
flat one
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